Magnetic speedometer



` 2o Figure 2.

Parenteel Mar. s, 1927.

UNITED STATESl PATENT OFFICE,

JOHN K. OLSEN, OF CHICAGO, ILLINOIS, .ASSIGNOR '1.0y STEWART-WARNER SPEEDOII- ETER CORIOIR'A'LION',l 0F CHICAGO, ILLINOIS, A CORPORATION OF VIRGINIA.

MAGNETIC srnnnomnrnn.

Application filed August 24, 1925. Serial No. 51,892.

The purpose of this invention is to provide an improved. construction in a magnetlc speedometer of the split ring type, particularly for economy and simplicity of assembling and dis-assembling the parts and for rendering the temperature compensating devices more reliably effective for` their purpose. It consists in the elements and feat tures of construction shown and described,

as indicated in the claims.

In the drawings: Figure 1 is a front elevation of a portion of a combined speedometer and odometer instrument presenting the speedometer parts,

the same being removedfrom the casing ot the instrument. Figurev 2 is a section at the line, 2-2, on' Figure 1.

Figure Sis a section at the line, 3-3, on

Figure 4 is a detail section 4.-4, on Figure 3. A

The structure .-shown in the drawlngs is that of a magnetic speedometer of the split ring type. y

The magnet is mounted for rotationby means of a stamping, 10, characterized by its formation in radial section, causing it to comprise a central trans-axial area, 10, centrally apertured at 10", for attaching it to at the line,

the shaft by which it is to be rotated as hereinafter described, and, successively encompassing said central area, are annular corrugatio'ns, 12 and 13, projecting in opposite` directions from the plane of said central area, 10, .the form of the outer circumferential annular area of the stamping being substantially cylindrical as seen at 15, and diametere'd to fit the interior diameter of the annular magnet and having the extreme edge -flexed outwardly in a transaxial flange, 16,

for seating the magnet; and for retaining the latter securely, lugs, 17 17, 17, are struck out of the. sheet metal at the crest of the outermost corrugation, and clinched outwardly around the upper corner of the mag-` one lamina of iron and the other of copperl or copper alloy, and is made from an L- shaped blank of which the shorter limb extends at right angles to the original plane of the blank, and the longer limb is coiled circularly to form a nearly closed ring as seen in Figure 3 with the iron lamina at the outer side of the coil and thereby at the under side of the radially extending limb, B1.

vThis thermostatic temperature compensator is mounted in the inner upwardly open side of the corrugation, 12, of the magnet mounting stamping, 10, spaced romboth sides of the channel of the corrugationfree from contact with either wall thereof as seen in Figure 2 with the radial limb, B1, extending out substantially parallel and slightly removed from contact with the upper surface of the magnet at the magnet gap, 21, over which the said radial limb extends at what may be regarded as the normal position, that is the position which it occupies at ordinary or average atmospheric temperature, say 60 F., said limb, B1, being spaced froml the magnet pole adjacent to which it extends far enough to avoid being iexed into contact with the magnet by the magnetic attraction of the magnet for the iron lamina of the compensator. The mountingand securement of the thermostatic compensator isveifectedV by lugs, b, b, formed projecting from the lower edge of the bi-m the end thereof, the m et mount, 10, having apertures at 16, 16, in the bottom of the channel of said inner corrugation, positioned to receive said lugs which are chnched over vori the opposite side ofthe stamping. The ends of the ring magnet facing ejach other at the gap, 21, are beveled in- "wardly with respect to the ring as seen in Figure 3 to cause the gap to be tapered widenin of the iii inwardly; and the radial limb, B1, I ermostatic lcompensatn is 1ongitudinally beveled as seen at b1 to` cause the edge which at normal temperature overhangs the ga-p, to trend at an acute angle to both edges of the gap and to' cross the edge past which said limb extends for overhanging the gap, substantially at the point at which the bevel of that edge begins.

It may be understood from the foregoing description that when the temperature of the instrument, including the magnet and the temperature compensator, exceeds that in view of which, as normal, the magnet and compensator are formed and related as described, the magnetic drag on the drag element is diminished,- requiring compensation to preserve accuracy of the speed indication; and that the same rise of temperature causing the bilaminate ring of the compensator to contract in radius by reason of the lamina, that of the outer,-iron-lamina, will cause the limb, B1, to be retracted circumferentially with respect to the magnet from over the magnetV gap which it overhangs, which will diminish the amount of flux conducted across the gap by said limb, and cause'a corresponding increase in the fiux cut Vby the drag element, thus offsetting the reduction of electric conductivity and consequent drag susceptibility caused by the rise in temperature. And it will be observed that at the same time that the limb, B1, is thus Withdrawncircularly, diminishing its overhang over the gap, it is by the saine cause flexed laterally and withdrawn laterally from the magnet, thus additionally.

compensating for the reduction of electric conductivity by the drag element caused by rise of temperature.

1. In a magnetic speedometer and the like in combination with a magnet rotor shaft, a metal stamping mount for the magnet hav- -ing a central area in a plane transverse to the rotor shaft centrally apertured for attachment to said shaft and having annular corrugations concentric with the rotor shaft protruding in opposite directions from ,the

plane of said central transaxial area and terminating as to its outer circumference yin a substantially cylindrical flange; a magnet diametered for seatin on said cylindrical flange, the latter having its terminal area flanged outwardly, and lugs flexed outwardly from the cylindrical tia-nge at a line parallel to said edge flange, the latter and said lugs gripping the magnet between them.

2. In a magnetic speedometer and the like in combination with the magnet rotor shaft and metal stamping mount for the vmagnet having a central area in a-plane transverse to the rotor shaft and centrally secured to the latter and having annular corrugations concentric with the rotor shaft protrudin in opposite directions from the plane of sai central transaxial. area; a ring magnet having a gap and mounted on and encompassing said mount; a thermostatic temperature compensator consisting of an integral biL laminate bar coiled With a radius approximating the mean radius of one of said corrugations of the mount and lodged therein and having at one end of the coil a limb extending transversely of the axis of the magnet and comprising a magnetically conducting part overhanging the magnet gap, said compensator being secured rigidly by the other end of the coilV to the bottom of the corrugation in the mount, whereby the coil is free to expand and contract radially within the limits of the Width of the corrugations and adapted to move as a unit by flexure from its said point of securement throughout its length to 'and including said gap-overhanging limb, for swinging the gap-overhanging l1mb more or less over the magnet gap.

3. In the construction defined in claim 2, `foregoing, the bilaminate compensator havmg one of its lamina of iron, said lamina belng at the side of the transversely extending limb which is toward the magnet, -for constituting the magnetically conducting part thereof. A 4. In a magnetic speedometer and the like 1n combination with the magnet rotor shaft, a metal stampingl mount for the magnet havlng a central area in a plane transverse to the rotor shaft and centrally secured to the latter and corrugated outside said trans- ,.axlal area; a ring magnet having a gap' mounted on and encompassing said mount; a thermostatic temperature compensator consisting of a bilaminate bar having onel of its laminae of iron, curved circularly with a radius approximating the mean radius etw-J' one of said corrugations of the mount secured at one pointof its circular extent rigldly to the mount and free from the point of ltslsaid securement to its more remote end, and by said securement positioned normally out of contact with either wall of the corrugation, whereby it is free to expand and contractradially within the limits of the width of the corrugation, said compensator having a limb 4extending transverselv to the rotor shaft and terminating overhanging the magnet gap, the iron laminae of said compensator being at the outer side of the coil and thereby atthe side of the limb adiacent to the magnet Where the latter overhangs the magnet gap. i

5. In the construction defined in claim 2, foregoing the thermostatic compensator bemg secured 1n the corrugation of the magnet mount by being formed with lugs projecting from the lower edge near the end to be secured, the mount having apertures in the bottom of the corrugation in which said lugs may be entered and clinched.

6. In a magnetic speedometer and the like, in combination with a magnet rotor shaft, a mount for the magnet and a ring magnet having a gap, mounted on and encompassing said mount; the mount having an annular depression; a thermostatic temperature compensator consisting of a bilaminate bar curved in circular form adapted to occupy said annular depression with clearance therein upon both sides, having 'its radius approximating the mean depression, said bar being secured by'one end rigidly to the mount, and having projecting from the other end a limb extending outwardly transversely to the rotor shaft and radius' of said annular v terminating partly overhanging the magnet gap from the side of said gap from which the circularly curved part of said bar extends circularly to the point of its securement to the. mount, said bilami'nate bar having one' lamina of iron and the circular part being curved with saidviron laminaat the,

outer side, whereby said iron lamina is atthe under side of said limb Which overhangs the magnet gap.

lin testimony whereof, have hereunto set my hand at' Chicago, illinois, this 12 day of August, 1925.

Jona K. oljisEN. 

